Journal of Catalysis 219 (2003) 206–213 www.elsevier.com/locate/jcat Low-temperature oxidation reactions of ethane over a Pt/Al 2 O 3 catalyst B. Silberova, a R. Burch, b A. Goguet, b C. Hardacre, b,∗ and A. Holmen a,∗ a Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway b School of Chemistry, Queen’s University of Belfast, David Keir Building, Stranmillis Road, Belfast BT 9 5AG, Northern Ireland, UK Received 24 December 2002; revised 20 March 2003; accepted 25 March 2003 Abstract Oxidative dehydrogenation of ethane was performed under conventional microreactor and TAP reactor conditions over a Pt/Al 2 O 3 catalyst between 100 and 600 ◦ C. During TAP studies, no ethene was produced whereas under flow conditions small but significant ethene formation was observed. This is consistent with a mechanism involving the gas-phase production of ethene rather than via a surface reaction. In compar- ison, both hydrogen and methane formation were found under TAP conditions and the trends with temperature and surface oxide composition are interpreted in terms of successive dehydrogenation steps on the catalyst surface. It is further observed that periodic introduction of the reactants can minimize deactivation processes.  2003 Elsevier Inc. All rights reserved. Keywords: Ethane; Oxidative dehydrogenation; Pt/Al 2 O 3 ; TAP 1. Introduction Light olefins such as ethene, propene, and butenes are important reactants widely used in numerous industrial processes. The current method of production is via steam cracking of a hydrocarbon feedstock [1] and although this process is widely applied, it has numerous shortcomings such as the high endothermicity of the reaction, long resi- dence times, and the production of coke on the reactor walls requiring periodic maintenance. In order to alleviate some of these issues, several studies have been performed to find an alternative catalytic route to the production of alkenes. In this regard, the partial oxidation of ethane has been investi- gated and shows considerable potential [2–18]. The products formed in this reaction are strongly depen- dent on the reaction conditions, such as the hydrocarbon:O 2 ratio, the catalyst used, and the temperature, and includes ox- idative dehydrogenation of ethane to ethene (ODH), partial oxidation of ethane to syngas (CO/H 2 ) and the total oxi- dation of ethane to carbon dioxide and water. Despite the * Corresponding authors. E-mail addresses: c.hardacre@qub.ac.uk (C. Hardacre), holmen@chemeng.ntnu.no (A. Holmen). number of studies performed on this reaction, the mecha- nism is still not fully understood. A number of investigations have reported high yields of ethene and propene obtained by oxidative dehydrogenation over Pt catalysts using very short contact times [11–18]. For example, Huff and Schmidt achieved selectivities to ethene up to 70% at conversions above 80% on Pt-coated foam monoliths, operating at contact times between 1 and 10 ms and high reaction temperatures (> 700 ◦ C) [13,14]. In these studies, Huff and Schmidt excluded homogeneous gas-phase reactions and a surface mechanism was suggested to explain the formation of ethene and propene. However, several other studies have shown that the high-temperature production of olefins could also be explained by the onset of homogeneous gas phase reactions [15–18]. Lødeng et al. found that oxida- tive dehydrogenation mainly proceeded in the gas phase and that the role of the Pt and Pt–Rh gauze catalysts used was to facilitate ignition of the reactants and therefore rapidly heat the reaction mixture [17,18]. This is in agreement with recent studies over a Pt monolith catalyst also indicating the importance of homogeneous gas-phase reactions at high temperatures [19]. In order to investigate the role of the catalyst, we have used a Temporal Analysis of Products (TAP) reactor [20] to probe the surface catalytic reactions during the oxida- 0021-9517/$ – see front matter  2003 Elsevier Inc. All rights reserved. doi:10.1016/S0021-9517(03)00150-7